Turbine blade



Patented Feb. 20, 1934 UNITED STATES PATENT OFFICE- No Drawing. Application October '7, 1930, Serial No. 487,083, and in Germany June 2,1928

4 Claims.

This invention relates to a special material for making steam turbine blades, shafts for large steam turbines and turbogenerators and other parts of machines to be subjected to similar kind of use. For this purpose hitherto nickel steels containing from 3 to 50 per cent'of nickel were used to a big'extent. These alloys generally contained from 0.2 to 0.4 per cent of carbon to secure a sufficiently high yielding point. It is well known that carbonaceous steels require a very careful heat treatment when being annealed or need for most purposes a careful double heat treatment by quenching and tempering. The mechanical properties obtained by such heat treatment are often afterwards annihilated by the fact that on soldering on the circumferential strips and soldering in the supporting wires the parts are heated anew and the cooling-down cannot be exactly controlled, whereby the mechanical properties obtained by the double heat treatment are again impaired. Moreover the resistance of nickel steels to corrosion and erosion does not come up to modern requirements.

Both disadvantages may be prevented according to my present invention by not employing carbon but molybdenum or tungsten as the constituent for increasing the yielding point. In the practically complete absence of carbon 2. much simpler and less delicate heat treatment is required and no deterioration of the mechanical properties results'from subsequent heating when the covering strips are soldered on or the supporting wires are soldered in. For example the notching bar impact test values are nearly the same after heating up to every temperature within a range from 650 to 1,100 degrees centigrade and cooling after heating at any desired rate from quenching to slow cooling within some hours. At the same time the resistance to corrosion and erosion is-considerably increased. In the absence of carbon, nearly the same values of strength are obtained by the addition of 2-5 per cent of molybdenum or 3-10 per cent of tungsten points by far superior to those of the carbonaceous nickel steels hitherto used and to the new nickel steels without carbon but containing molybdenum or tungsten. It is true that such nickel steels containing, besides carbon, molybdenum or tungsten again require a more careful heat treatment.

The desired properties may be attained by adding either tungsten or molybdenum or both metals. The same properties may be attained by substituting aluminum for a part of the whole of either the molybdenum or tungsten or of both metals. 0.1 to 4 per cent of aluminum may be employed.

l. A turbine blade made of an alloy consisting of iron 46 to 98.5%, nickel 39 to 0.5%, metals of the sixth group of the periodic system of the elements having a melting point above 2,000 C.

15 to 1%, and carbon less than 0.04%.

2. A turbine blade made of an alloy consisting 35 of iron 46 to 98.5%, nickel 39 to 0.5%, tungsten 15 to 0.5%, and carbon less than 0.04%.

3. A turbine blade made of an alloy consisting of iron 53 to 98.5%, nickel 39 to 0.5%, molybdenum 8 to 0.5%, and carbon less than 0.04%.

4. A turbine blade made of an alloy consisting of iron 46 to 97.5%, nickel 39 to 0.5%, molybdenum 7 to 0.5%, tungsten 14 to 0.5%, the sum of the percentages of molybdenum and tungsten not exceeding 15%, and carbon less than 0.04%.

' WILl-IELM norm. 

